In known plants for converting solar energy into electrical energy, it is known that the items which have a high associated cost, and which therefore have a profound impact on the overall cost of the plant, are the photovoltaic cells, forming “solar panels” which, when irradiated, convert solar energy into electrical energy by virtue of the material from which they are made and which contains silicon. Several photovoltaic cells connected together are referred to as a “module” or “panel”, and the latter are connected in series in the intended area. The various modules can be easily dismantled, or separated from one another, thereby giving the plant flexibility for adding or removing, as desired, the modules in order to vary as needed the production of electrical energy and to customize the plant itself. Plants of differing power levels can thus be produced with the same type of module.
Conversion plants are generally installed in areas exposed to the sun, outdoors (on roofs, on patio areas, on the ground, etc.), and may cover extensive surface areas.
Due to the modular nature of panels, and their high cost, there is a substantial problem of theft of panels inside plants. Indeed, the panels can easily be resold and reused without modifying them.
To address this drawback, since constant monitoring by security officers of plants is extremely costly, which plants may even be in locations that are remote or difficult to access, standard antitheft systems that are also employed in other fields are used in the prior art, for example the use of closed circuit television cameras.
However, even this type of antitheft monitoring system is particularly expensive, especially in the case of small plants and/or ones for domestic use, in which the antitheft system would arrive at a cost of the same order of magnitude as that of the conversion plant.
A monitoring system for monitoring possible malfunctions of a solar plant is described by EP 1 326 286, and U.S. Pat. No. 6,545,211, nevertheless such systems are not suitable for functioning as anti theft system.
Moreover the system according to EP 1 326 286 is so configured as to function only during solar irradiation, i.e. during the functioning of the solar plant.
Moreover, JP 2000 164906, describes a theft detection circuit for solar battery comprising a current supply sources separated form solar batteries, and theft sensing detecting circuit by means of which a current is made to flow through solar batteries.
The system according to JP 2000 164906 may be used only at low voltage level and requires a dedicated power system.
Therefore the need arises of an anti theft system for solar cell plant being reliable, and having low energy consumptions.
Moreover an anti theft system is required so configured as to function either during solar irradiation and also during night or when no solar irradiation reach the cells.